Thursday, January 28, 2010

I indulge in baseball stats. While I don't consider this a purely statistical analysis site, I do my fair share of it and reference "advanced stats" on a regular basis.

But I get annoyed by my Sabermetric brethren from time to time as they introduce new stats and pronounce them the new standard. This doesn't work for me because while they may measure a snapshot of performance or add predictive value, there is typically no frame or reference. Specifically, historical reference. I recently joined Baseball Prospectus and while I enjoy the writing, they use a ton of proprietary stats that are not available to the general public, only their subscribers. There's no frame of reference among the average baseball fan so you are just talking to yourselves.

FanGraphs.com recently unveiled a new stat call wRC+ (Runs Created based on wOBA compared to league average). Many stat guys declared this as the new stat to use and that OPS+ was now irrelevant. This irritated me as I thought to myself, "But where's the frame of reference? What was Babe Ruth's career wRC+?"

But then I realized that I use stats on my posts here that many may not understand or have a reference for. So shame on me.

With that in mind, here's a quick tutorial for stats I regularly reference on the site, as well as links to pages that offer more detail and/or historical context.

The Slash Line

I often refer to a player's "line" is my posts. Brian Roberts' line for 2009 was .283/.356/.451. The slash line here signifies Batting Average/On-base Percentage/Slugging Percentage. It's a quick way to sum up a player's offensive production.

OPS

OPS is simply On-base Percentage plus Slugging Percentage. For reference, Babe Ruth has a career 1.164 OPS. Frank Robinson had a career .926 OPS. Nick Markakis has a career .838 OPS.

OPS+ lets you compare offensive output across different eras. Let's face it; a guy who hit .300 with 20 home runs in 1967 is far more impressive than a guy who did the same thing in 1997. OPS+ measures a player's OPS vs. the average OPS for the league that season. It helps to compare players across different eras.

Babe Ruth's career OPS+ is 207. Frank Robinson has a 154 career OPS+. Nick Markakis' career OPS+ is 119.

A more detailed explanation of OPS+ can be found here. Career OPS+ leaders are here and Single Season OPS leaders are here.

WAR

WAR is Wins Above Replacment and is a measure of how many "wins" a player can contribute above the average "replacement level" player in his league. This was recently explained very well in this ESPN article by Matt Klaasen and Dave Cameron of FranGraphs.com.

Babe Ruth has a career WAR of 172.0. Frank Robinson's is 107.1. Nick Markakis has a carrer WAR of 15.1.

ISO is isolated power, a stat that I love to use. ISO measures the "raw power" of a hitter as it separates the batting average component from the slugging percentage. It is basically the slugging percentage minus the batting average but the more exact calculation is:

Total Bases - Hits/At Bats

Babe Ruth had a carrer ISO of .348. Frank Robinson comes in at .243. Nick Markakis has a career ISO of .173.